1. Field of the Invention
This invention relates to heating appliances, especially radiators, and more particularly to a method and apparatus for making a water-tight radiator element of the type produced from a flat tube having open ends which are closed and welded.
2. Description of the Related Art
In prior art methods of making such radiator elements, the open ends of the flat tube are closed by means of sealing covers which are inserted in the respective tube ends and welded to the sidewalls of the tube. In other such elements, a filler part is inserted in the flat tube near each open end and likewise welded or soldered to the sidewalls.
A radiator having flat elements disposed parallel to one another is described in U.K. Patent Application No. 2,094,966 A. Support parts forming the closure walls of the flat elements are inserted in the open ends of the latter and welded to the sidewalls.
None of these prior art methods yields a clean and symmetrically shaped radiator element. Moreover, the welding seams must be ground smooth when a sealing cover is inserted as well as when a filler or support part is introduced into the flat tube.
French Pat. No. 2,475,708 describes a radiator having flat elements disposed parallel to one another, the ends of which are sealed by bending the edge portions of the opposing wide side surfaces of the flat tube toward the middle of the ends and then welding them to one another. Sealing is not accomplished by means of rollers, however. Here, too, the surface of the bent edge portions with the welding seam is not cleanly formed.
In another prior art radiator element of this type, the open ends of the flat tube are closed by means of rollers and a support mandrel, whereupon the closed element is welded. One drawback of this method is that because of the opening for the mandrel, the element is not completely closed and is therefore not suitable for further processing by means of pressing and welding.